There are 3 of them:
Do I understand it correct - "writeback" provides best performance and you can lose data easily. "Journal" provides worst performance and best data protection. "Ordered" is something between them, average.
To mount ext4 is fstab in "journal" mode should I save the line as
/dev/sda2 / ext4 defaults,data=journal 0 1
Do I need "defaults" here?